TiAl基合金組織演變與室溫拉伸變形的研究.pdf

1、中南工業(yè)大學博士學位論文TiAl基合金組織演變與室溫拉伸變形的研究姓名：唐建成申請學位級別：博士專業(yè)：材料學指導教師：黃伯云2000.5.1ABSTRACTMicrostructuralevolutionroomtemperaturetensilepropertiesandroomtemperaturedeformationmechanismofTi47舢2Cr(m01％)weresystematicallystudiedbymeans

2、ofopticalmicroscopyscanningelectronmicroscopy(SE～O，transmissionelectronmicroscopy(TEM)andtensiletestsThroughinvestigatingdiscontinuouscoarseninginascastTiAlbasedalloythreetypesofmorphologyofdiscontinuouscoarseningareobse

3、rvedinfullylamellarTiAlbasedalloyAtthesametime，itisfoundthatincreasingheattreatmenttemperaturepromotesthediscontinuouscoarseningprocessThroughinvestigatinggraingrowthanditskineticsofaforgedTiAlbasedalloyduringheattreatme

4、nt，itisfoundthatthegrainsizeoftheTiAlbasedalloyisdependentonheattreatmenttemperatureandholdingtimeThroughanalyzingtheformationmechanismoflamellaeandthefactorsthataffectthelamellarspacingintheTi舢basedalloyduringcontinuous

5、cooling，anexpressionofthelamellarspacinghasbeenderivedusingtheledgemechanismoflamellaegrowthItisshownthatthelamellarspacingisinverselyproportionaltocoolingrateandincreaseswithdecreasingcolonysizeandincreasingAIcontentFin

6、efullylamellarmicrostrueturewithgoodcomprehensivemechanicalpropertiesismadeItstensilestrengthyieldstrengthandductilityreach728MPa，650MPaand27％respectivelyUsingdoubletemperatureheattreatmentfineuniformduplexmicrostructure

7、withhighductilityismadeItstensilestrengthyieldstrengthandductilityreach632MPa547MPaand35％respectivelyThroughanalyzingtherelationshipbetweenmechanicalpropertiesandmicrostructuresoffllllylamellarTiAI—basedalloyitiSfoundtha

8、titstensileductilityatroomtemperatureincreaseswithdecreasingcolonysizeandlamellarspacingandksyieldstrengthandtensilestrengthatroomtemperatureareinversesquarerootdependenceoncolonysizeandlamellarspacingThroughTEManalyzing